The period from the end of the Cretaceous until the present day extended through about 65 million years. Within this time two major changes took place. The first was the continual increase in the numbers and diversity of the flowering plants culminating in their important role as purveyors of many classes of substances to the human race. The second was the dramatic deterioration in the world’s climate reaching a nadir in the Ice Age which ended about ten thousand years ago. Even with the end of the Ice Age the climate of the regions of the world which are up to about 3,500 miles from the North or South poles never reverted to what it was 65 million years ago.
At that time, the climate of the region which is now the Thames Estuary in south-east England was so warm that it supported a dense tropical flora with many plants that at the present day only grow in the equatorial forests of the Indo-Malay region of south-east Asia. Admittedly continental drift had not yet moved southern England up to its present latitude of 51 degrees North. It was then at about 35 degrees North; that is to say about where the Mediterranean region is now. Nonetheless southern France and Italy certainly do not support a tropical flora and there is still a marked contrast between their vegetation and that of south-east Asia.
The Thames Estuary flora was remarkable for two reasons. Firstly, it indicated the existence of a tropical flora some two thousand miles north of the equator and secondly there were a substantial number of flowering plants. Over 300 species of fossil seeds and fruits have been discovered. This number provides a measure of the variety of flowering plants that were available to form a complex flora at this time. Conifers are mainly represented by large numbers of twigs. Crocodiles flourished in the river and its tributaries. All in all, it was a prime example of a lush tropical forest growing well into the Northern hemisphere under a climatic regime very different from that of the present day.
After this time, the world climate declined in average temperature gradually until about 15 million years ago when ice caps formed at the poles. These steadily increased in area so that forest growth was forced away from the polar regions and a zone of vegetation known as tundra started to form around the Arctic Ocean. About 2 million years ago the Ice Age began and ice gradually spread south to the Great lakes in North America and to the south of England in Europe.
The furthermost limit of glaciation ebbed and flowed with changes in the average temperature until finally the ice receded to the well-known limits shown in modern atlases. Because Great Britain became cut off from continental Europe by the formation of the English Channel, the plants that managed to migrate back when the ice melted represent only a fraction of the flora that was forced out by the ice. Also, on some of the highest peaks in northern Scotland there are relict glacial floras that have not been ousted by plants returning from continental Europe because the local mountain-top climate is so inhospitable. The present ice limits have been maintained for about 10,000 years.
Human ancestry has been traced back a few million years into parts of East Africa. Although the early hominoids undoubtedly supported themselves to a large extent by killing various animal species, they must also have made use of any flowering plant products that came to hand, particularly if they were available at times when animals proved difficult to catch. From these very early times in human history the reliance of humans on flowering plants has grown steadily. It would be very difficult at this time to visualize how humans could manage without them. Especially now that an entire cult of vegetarianism has become widely established. For those unfortunate individuals who cannot obtain much animal protein, vegetarianism is an enforced way of life. If one wanted an example of how little the non-flowering plants provide in the way of human food, a walk through a typical conifer plantation illustrates the point exactly.